Virtual machines can be provided in a computer to enhance flexibility and performance. A virtual machine typically refers to some arrangement of components (software and/or hardware) for virtualizing or emulating an actual computer, where the virtual machine can include an operating system and software applications. Virtual machines can allow different operating systems to be deployed on the same computer, such that applications written for different operating systems can be executed in different virtual machines (that contain corresponding operating systems) in the same computer. Moreover, the operating system of a virtual machine can be different from the host operating system that may be running on the computer on which the virtual machine is deployed.
In addition, a greater level of isolation is provided between or among applications running in different virtual machines. In some cases, virtual machines also allow multiple applications to more efficiently share common resources (processing resources, input/output or I/O resources, and storage resources) of the computer
Normally, when a physical machine is powered down (either shut off or placed into a lower power mode), any virtual machine running in such a physical machine is also shut off or otherwise disabled or made unavailable. The particular physical machine that was shut off or otherwise placed into lower power mode can be part of a network of physical machines. Disabling of virtual machines on the particular physical machine may be an unexpected event that may disrupt or adversely affect operation of other physical machines or the overall system.